Sizing polyolefin yarns with aqueous atactic polypropylene emulsion



United States Patent SIIZHNG PULYOLEFIN YARNS WITH AQUEUUS ATACTIC POLYPROPYLENE EMULSKON Walter B. Armour, Plainfield, and Herbert C. ()lsen,

Berkeley Heights, N.J., and Michael P. Diamantopoulos, South Acton, Mass, assignors to National Starch and Chemical Corporation, New York, N.Y., a corporation of Delaware No Drawing. Filed Mar. 25, 1963, Ser. No. 267,790 9 Claims. (Ci. Zed-49.6)

This invention relates to novel compositions for the sizing of polyolefin yarns and filaments as well as to the materials sized therewith. More specifically, this invention relates to the sizing of polyolefin yarns and filaments with compositions which provide these materials with improved tensile strength, compactness, smoothness, and resistance to abrasion.

The sizing of yarns and filaments is a process involving the coating or impregnation of said yarns and filaments with a suitable sizing agent which may be in the form of either a lacquer or an aqueous solution or dispersion. This sizing operation is necessary in order to substantially strengthen the yarns and filaments so as to enable them to withstand subsequent processing operations. Aqueous dispersions of starch and starch derivatives have generally been utilized to size cotton and other natural fibers. The use of such starch-based dispersions, however, has not been applicable to the sizing of synthetic fibers and filaments. Thus, the use of starches and their derivatives for the sizing of synthetic fibers and filaments is effectively limited by the stability and viscosity variations of their dispersions and also by their rather limited affinity for the material to which they are being applied. The inadequacies of these starch-based dispersions have therefore led to the use of expensive and only partly effective polymeric materials, such as polyvinyl alcohol,

polyacrylic acid, polymethacrylic acid, and the like, as

sizing agents for synthetic fibers and filaments.

The improved properties of the recently developed yarns and filaments based on polypropylene and other polyolefins, such as polyethylene, have made it highly desirable to attempt to use these yarns and filaments in an increasing variety of applications in the textile field. Thus, it has been found that polypropylene yarns and filaments possess a relatively low specific gravity and consequently provide a lightweight material of high coveringability. Moreover, these polypropylene materials possess highly desirable properties of strength and smoothness. However, despite the enhanced properties of polypropylene yarns and filaments the extent of their use has been C11 C31 CH3 CH3 CH3 CH3 CH3 Clil3 C513 CH3 na na na somewhat curtailed due to the lack of a satisfactory sizing agent for the polypropylene. Similarly, other polyolefin yarns and filaments have not been widely utilized 3,262,899 Patented July 26, 1966 because of the inadequacies of the sizing agents of the prior art.

It is thus an object of this invention to provide a method for the sizing of polypropylene and other polyolefin yarns and filaments. It is a further object of this invention to provide a novel sizing composition for polypropylene and other polyolefin yarns and filaments which imparts improved properties of strength and resistance to abrasion thereto. Other objects and the advantages of this invention will be apparent from the following description thereof.

For the purposes of this invention, reference will be made hereinafter only to treatment of polypropylene yarns and filaments. It should be noted that such reference is not intended to restrict the scope of our invention, but is merely made in light of the greater extent of textile usage which polypropylene currently enjoys, as compared to other polyolefins. Therefore, it is to be understood that whenever reference is hereinafter made to polypropylene, such reference also comprehends the use of other polyolefinic materials, including mixtures of polyolefins as well as copolymers of olefins with various ethylenically unsaturated comonomers.

Moreover, it should also be understood that for the purposes of this invention, whenever reference is made to the term polypropylene yarn, said reference is meant to be equally applicable to the use of polypropylene filaments. Thus, the sizing compositions of our invention may be applied to polypropylene filaments as well as to yarns wherein the polyolefin filament may be only one component of the composite yarn.

In accordance with our invention, polypropylene yarns or filaments are sized with a novel sizing agent comprising chlorinated atactic polypropylene. The polyolefin materials thus treated with chlorinated atactic polypropylene have been found to display characteristics of enhanced tensile strength, compactness, smoothness, and resistance to abrasion.

Polypropylene is a synthetic resin which, of late, has enjoyed greatly increased usage in the preparation of molded articles, fibers and films. For use in the latter applications it is desirable that the polypropylene should have a highly crystalline structure which thereby serves to increase the strength of this versatile plastic. The inherent crystallinity of polypropylene is, in turn, dependent upon its molecular structure or configuration. Thus, crystalline polypropylene molecules will exhibit a socalled isotactic structure wherein the methyl groups will be regularly distributed on the same side of the polymer chain in a manner analogous to that shown in the following diagram:

iii

On the other hand, polypropylene which is not crystalline will exhibit a so-called atactic structure wherein the methyl groups are randomly distributed on either side of CH CH CH CH CH In manufacturing polypropylene, the processes currently employed make use of so-called stereospecific catalysts which are chosen for their ability to provide the resulting polypropylene with an isotactic structure and thereby impart a maximum degree of crystallinity to the polymer. However, despite the use of these catalysts, present polymerization techniques still produce a product with a significant proportion of atactic polypropylene. The presence of this non-crystalline fraction would, of course, detract from the strength of any articles manufactured from such polypropylene. Therefore, it is the practice in the art to separate this atactic portion from the crystalline material and this is readily accomplished by means of a solvent extraction technique.

The chlorinated atactic polypropylene which is used as the sizing agent in the process of our invention is prepared by dissolving the atactic polypropylene in a non-reactive organic solvent such as carbon tetrachloride, methylene chloride, chlorobenzene, or chloroform. The atactic polypropylene is then chlorinated in the presence of a suitable catalyst which may be a solvent soluble organic peroxide, such as benzoyl peroxide or lauroyl peroxide, or a metal salt, such as ferric chloride or aluminum chloride. The latter catalysts are usually present in the reaction mixture in a concentration of about 0.1 to 1.0%, by weight, of the atactic polypropylene undergoing chlorination. Chlorination may be accomplished by bubbling chlorine gas directly into the reaction mixture or by refluxing the latter in the presence of a chlorination agent such, for example, as sulfuryl chloride or thionyl chloride.

For use as a sizing agent in the process of our invention, the chlorinated atactic polypropylene may contain from about 8 to about 35%, by weight, of chlorine.

A typical procedure, in this case employing sulfuryl chloride, which may be utilized for the chlorination of atactic polypropylene would involve first preparing an organic solvent solution of the atactic polypropylene with the process of solution being assisted by subjecting the mixture to mechanical agitation as well as by heating it to reflux. While the thus prepared solution is maintained under reflux and agitation, the selected catalyst is introduced therein. The sulfuryl chloride is then slowly added with the solution being maintained at reflux for a period which may range from about 5 to 10 hours, thereby yielding the desired chlorinated atactic polypropylene. It may be noted that the above described chlorination procedure may also be utilized with thionyl chloride. However, when gaseous chlorine is used, this procedure is modified somewhat in that the reaction temperatures are maintained below reflux levels.

The chlorinated atactic polypropylene utilized in the process of our invention may be aplied to polypropylene yarns in the form of the organic solvent solutions Wherein they were prepared or in the form of an aqueous emulsion. In preparing such emulsions, the lacquers may be readily emulsified by adding an aqueous solution of an emulsifier, such as polyvinyl alcohol, morpholineoleic acid mixtures, and the like, to the lacquer while the lacquer is vigorously agitated. Any of the conventional means generally used by the practitioner for the sizing of yarns may be employed in our process. Thus, for

CH2 c c c CH2 CH2 CH2 example, the polypropylene yarn may be passed through a bath comprising an aqueous emulsion of our novel sizing composition, then through a set of squeeze rolls in order to remove excess size, and finally, through a drying chamber or over the surface of internally heated drying cylinders called cans. For most purposes, the chlorinated atactic polypropylene should be applied to polypropylene yarns in a concentration ranging from about 1% to about 10% of resin solids as based on the weight of dry yarn. The resin solids content of the sizing compositions may vary considerably depending upon a number of factors, including the number of filaments in each yarn, the construction of the fabric into which the yarn is to be woven, loom speeds, and similar variables related to the sizing and weaving processes.

The chlorinated atactic polypropylene sizing agents of our invention may be used as the sole sizing agent for polypropylene yarns or, if desired, they may also be formulated with other sizing agents. In general, the chlorinated atactic polypropylene is used as the sole sizing agent in those cases where it is to be applied to polypropylene filament yarns. However, when polypropylene spun yarns are to be sized, it may also be formulated with conventional sizing agents, such as starches, polyvinyl alcohol, polyacrylic acid, and the like.

Various additives, e.g., oils and lubricants, may also be incorporated in the sizing compositions of our invention. It should be noted, however, that the characteristics of chlorinated atactic polypropylene make the inclusion of such additives unnecessary in order to achieve satisfactory sized yarns.

In the following examples, which further illustrate the embodiment of our invention, all parts given are by weight unless otherwise indicated.

Examples The following examples illustrate the sizing of polypropylene yarn using the novel sizing compositions of our invention.

Using gaseous chlorine and sulfuryl chloride as chlorination agents, we prepared several chlorinated atactic polypropylene lacquers each of which had a resin solids content of 25%, by weight. In preparing these lacquers, the chlorination procedure described hereinabove was utilized. The resulting lacquers were then converted into aqueous emulsions by adding an aqueous solution of an emulsifier to the lacquer while subjecting the latter to vigorous agitation. In each case, we used 6%, of emulsifier as based on the weight of chlorinated atactic polpropylene in the respective lacquers. These emulsions, each of which had a resin solids content of 5%, by weight, were then used to size polypropylene yarns by means of a process in which the yarns were first passed through a bath containing the emulsion Whereupon the wetyarns were then passed through a set of squeeze rolls to remove excess sizing material, and were thereafter dried on heated cans which were maintained at a temperature of about 200 F.

The polypropylene yarn sized according to the method set forth above was then tested in order to determine its strength characteristics. In testing the yarn, an instrument known as the Duplan cohesion tester was utilized. This device consists of a mechanically propelled friction plate which moves back and forth over the sample of sized yarn while the latter is tightly laced between a series of porcelain hooks. Upon noticing a partial separation or fraying of the yarn, note is made of the number of cycles which have elapsed. The separation of the yarn, in this manner, indicates that the protective action of the size has been lost. Thus, the number of cycles which each sample withstands is a direct indication of the sizing efficiency of the particular sizing composition used.

In the following table are presented details relating to the preparation of the various atactic polypropylene lacquers and their subsequent conversion to aqueous emulsions as well as the results obtained in the above described cohesion strength tests.

tic polypropylene being prepared by chlorinating an organic solvent solution of a-tatic polypropylene in the presence of a free radical catalyst.

3. The method of claim 1, wherein the amount of chlorine in said chlorinated atactic polypropylene ranges from 8 to 35% by weight.

4. The method of claim 1, wherein said chlorinated atactic polypropylene is applied to said polyolefin yarns in a concentration ranging from 1 to 10% by weight of resin solids, as based on the weight of the dry yarns.

5. The method of claim 1, wherein said polyolefin yarn is selected from the group consisting of polypropylene and polyethylene yarns.

6. A polyolefin yarn sized with chlorinated atactic Formulation Parts of Atactic Abrasion Parts of Chlori- Percent Chlo- N o. Polypropylene Catalyst Used (Parts) Cycles Chlorination Agent nating Agent rine in Chlori- Emulsiiying Agent nated Polymer 100 Lauroyl peroxide (0.3) 120 Suliuryl chloride 220 Polyvinyl alcohol. 100 Ferric chloride (0.3) 400 lorine 94 26 Do. 100 Ferric chloride and 300 do 60 18 D0.

iodine (0.3) (0.1). 100 Ferric chloride (0.3) 600 do 11 0lleic acid-morphm me. 100 Ferric chloride (0.3) 600 do 30 8 Polyvinyl alcohol.

The number of abrasion cycles withstood by the yarn sized with our polymer formulations was considerably higher than the number withstood by yarn sized with conventional sizes. Thus, for example, the maximum number of cycles withstood by polypropylene yarn sized, respectively, with solutions containing 5%, by weight of resin solids, of polyacrylic acid and polyvinyl alcohol, usually were no more than about 20. It can thus be seen that the use of our sizing formulation olfers significant advantages over the sizes previously employed.

Any departure from the above description which conforms to the present invention is intended to be included within the scope of the invention as defined by the following claims.

We claim:

1. A method for sizing polyolefin yarns which com prises applying chlorinated atactic polypropylene to said yarns by passing said yarns through an aqueous emulsion of said chlorinated atactic polypropylene and thereupon drying the thus treated yarns.

2. A method for sizing polyolefin yarns which comprises applying chlorinated atactic polypropylene to said yarns by passing said yarns through an aqueous emulsion of said chlorinated atactic polypropylene and thereupon drying the thus treated yarns; said chlorinated atacpolypropylene, the surface of said yarn being coated with said chlorinated atactic poly-propylene.

7. A polypropylene yarn sized with chlorinated atactic polypropylene, the surface of said yarn being coated 30 with said chlorinated atactic polypropylene.

8. A polyethylene yarn sized with chlorinated atactic polypropylene, the surface of said yarn being coated with said chlorinated atactic polypropylene.

9. The polyolefin yarn of claim 6, wherein the amount 3 of chlorine in said chlorinated atactic polyolefin ranges from 8 to 35% by weight.

References Cited by the Examiner UNITED STATES PATENTS MURRAY TILLMAN, Primary Examiner. SAMUEL H. BLECH, Examiner. W. J. BRIGGS, SR., Assistant Examiner. 

1. A METHOD FOR SIZING POLYOLEFIN YARNS WHICH COMPRISES APPLYING CHLORINATED ATACTIC POLYPROPYLENE TO SAID YARNS BY PASSING SAID YARNS THROUGH AN AQUEOUS EMULSION OF SAID CHLORINATED ATACTIC POLYPROPYLENE AND THEREUPON DRYING THE THUS TREATED YARNS. 